Lossius I, Krüger P G, Male R, Kleppe K
Mutat Res. 1983 Apr;109(1):13-20. doi: 10.1016/0027-5107(83)90090-8.
The influence of low concentrations of mitomycin-C on the structure of the envelope-free nucleoid was studied in several strains of Escherichia coli K12. The wild-type strain AB1157 uvr+ rec+ and 3 mitomycin-C-sensitive derivatives carrying mutations in the uvrA, uvrB and recA genes, were used. Treatment of the control strain with mitomycin-C, 0.5 microgram/ml, followed by incubation in drug-free medium resulted in the formation of a transient fast-sedimenting nucleoid with a sedimentation coefficient of 2200 S. A fraction of 25% of the nucleoids had attained the normal sedimentation coefficient of 1570 S 3 h after removal of mitomycin-C. With the uvr- strains, mitomycin-C induced a slow, almost linear increase in the S value of the envelope-free nucleoid. In these cases the S value continued to increase during post-incubation and was 2050 S 3 h after removal of the drug. Post-incubation of recA- cells resulted in loss of supercoiling, decrease in S value of the nucleoid and degradation of DNA. Results obtained with phase-contrast and electron microscopy were in good agreement with the hydrodynamic data.
在几种大肠杆菌K12菌株中研究了低浓度丝裂霉素C对无包膜类核结构的影响。使用了野生型菌株AB1157 uvr+ rec+以及3种在uvrA、uvrB和recA基因中携带突变的丝裂霉素C敏感衍生物。用0.5微克/毫升的丝裂霉素C处理对照菌株，然后在无药物培养基中孵育，导致形成一种沉降系数为2200 S的瞬时快速沉降类核。在去除丝裂霉素C 3小时后，25%的类核达到了1570 S的正常沉降系数。对于uvr-菌株，丝裂霉素C诱导无包膜类核的S值缓慢且几乎呈线性增加。在这些情况下，S值在孵育后继续增加，在去除药物3小时后为2050 S。recA-细胞的孵育后导致超螺旋丧失、类核S值降低和DNA降解。相差显微镜和电子显微镜获得的结果与流体动力学数据高度一致。
